From the prior art there is known a ‘flying hoverbike’ (see patent RU 108016, 29 Oct. 2010) with a parachute recovery system, comprising a cruciform airframe, 4 symmetrically located propellers and an engine. The disadvantage of the said flying vehicle is that its airframe is a flat-type beam and it does not provide sufficient structural rigidity which is necessary for the whole structure to be resistant to precision oscillation and nutation oscillation generated by heavy propellers. This, in turn, causes resonance oscillation to appear and lead to fatigue defects of the airframe which makes the task of flight stabilization rather difficult. If at least one propeller out of four fails (and any other structural elements associated with the functioning of the propellers), it causes the flying vehicle to crash, its parachute recovery system is unable to prevent the accident and only mitigates the consequences. The efficiency of the parachute recovery system is doubtful for low flight altitudes. Heavy propellers of large diameter cannot be stopped quickly in emergency.
Additionally, from the prior art there is known a flying hoverbike designed by Aero-X Hoverbike comprising a combustion engine and two propellers for takeoff thrust, as well as a flight steering system with aerodynamic control surfaces. The disadvantage of the said flying vehicle is that both of its propellers are driven from the same engine, a double-propeller layout is not so reliable, any engine failure or any malfunction of propellers, transmission, aerodynamic control surfaces or other related systems will cause spinning of the flying vehicle during the flight making it impossible for the pilot to escape and for the flying vehicle to be rescued. Flat-type beam does not provide the structural rigidity necessary to withstand the precision and nutation oscillation generated by heavy propellers. This causes the resonance oscillation to appear, as well as fatigue defects in the airframe which makes the task of flight stabilization rather difficult. Heavy propellers of large diameter cannot be stopped quickly in emergency.
One more example from the prior art is a flying hoverbike designed by MA hoverbike helicopter available in various configurations—with two or four propellers. The disadvantage of the said flying vehicle is that both of its propellers are driven from the same engine, a double-propeller layout is not so reliable, any engine failure or any malfunction of propellers, transmission, aerodynamic control surfaces or other related systems will cause spinning of the flying vehicle during the flight making it impossible for the pilot to escape and for the flying vehicle to be rescued. The same is applicable for the 4-propeller embodiment, the flying machine cannot continue flying if just one propeller fails. Flat-type beam does not provide the structural rigidity necessary to withstand the precision and nutation oscillation generated by heavy propellers. This causes the resonance oscillation to appear, as well as fatigue defects in the airframe which makes the task of flight stabilization rather difficult. Heavy propellers of large diameter cannot be stopped quickly in emergency.
There is another flying vehicle called “Moller M200G Volantor” (US), comprising a platform, a fuselage, eight rotary piston engine (the Wankel engine), eight propellers installed circumferentially, a cockpit with a pilot seat. The disadvantage of the said vehicle is that it has a single fuel supply system and a fuel tank feeding all of the eight engines, so the failure of the fuel supply system would immediately cause all the engines to stop. Autorotation landing is not possible for this vehicle because of smaller impellers and low deceleration force of the engines, therefore, flight safety by means of engine redundancy is not ensured. The Wankel engines are known as rather complicated to control, because of higher acceleration time as compared with electric engines. It is also necessary to keep high engine rpm in order to maintain better engine performance. These engine features underlie the use of propeller pitch control system. This add-on makes the flying vehicle heavier and less reliable, it also means more maintenance due to one more serviceable unit installed on each of the engines. All those disadvantages of propulsion system cause the flying vehicle overswinging even in calm air (which is pretty well noticeable in the published videos where the tests of the flying vehicle are shown) which is likely to cause loss of hold during the flight and finally leads to the accident. Frequent overheating and engine fire were the reason why the flying vehicle designer changed the type of fuel: they replaced petrol with toxic ethanol-water mixture. This change did not help to overcome the fire hazard issue, but negatively affected the power-to-weight ratio and engine acceleration time. Among the disadvantages which prevented this invention to be launched into serial production were the following: low reliability, short service life and maintainability of the Wankel engines and propeller pitch control system, low producibility of the flying vehicle, clumsy design of the flying vehicle—bowl-shaped with high windage, lack of foldability features together with increased cost.
Another known example is a VC200 flying vehicle offered by e-volo, comprising 16 horizontally installed electric engines with propellers, a cockpit with a charging battery inside, and a parachute recovery system. Among the disadvantage of the most similar product are: interdependent power system with all the engines supplied by the same battery and with extensive power wiring between the battery and the engines which does not ensure the flight safety via redundancy, because failure of the battery causes all of the engines to stop at the same time, while small diameter of propellers and low engine deceleration force make the autorotation landing impossible. The fuselage design with fracture susceptible carbon members (with dia. over 10 meters) of the flat structural airframe where the propellers are installed make the flying vehicle heavier without solving any design task. The combination of the above disadvantages increases the cost of the flying vehicle and has negative impact on its maintainability. Aviation-type controls require the pilot to have the helicopter piloting skills. The efficiency of the parachute recovery system is doubtful for low flight altitudes.